Material handling systems often employ conveyers to move articles from one location to another. Gravity conveyers are inclined downward to move articles on rollers with the force of gravity. Gravity conveyers are reliable and inexpensive, but they do have a significant limitation. They only work when material is being moved from an upper location to a lower location.
In large installations, this limitation inhibits the extended use of gravity conveyors, and to solve these problems, inclined powered conveyers are at times used. While inclined powered conveyers will move articles in an upward direction along a controlled incline, they require a lot of space to raise an article to a desired height.
Vertical lift conveyers move articles from an inlet conveyer to an outlet conveyer at a different height in a limited space. Vertical lift conveyers typically employ a horizontal platform which is driven in a continuous rectangular path of travel by actuation of chain, belts or cable.
The horizontal platform includes spaced arms which are aligned to pass between spaced inlet conveying means adjacent to the inlet conveyer in an upward vertical path to lift an article from the inlet conveying means. The horizontal platform follows the rectangular path of travel and deposits the article on the downward vertical path onto the outlet conveying means adjacent to the output conveyer. One or more horizontal platforms may be secured to the drive means in spaced relation, to provide multiple lift capacity during the continuous rectangular path of travel of the drive means.
Where cantilevered platforms have been used to lift articles between levels in a rectangular path of travel, additional guide means, track, brackets, etc. have been required to maintain the platform in a horizontal position during its rectangular path of travel. These additional guide means are normally offset from the point of connection of the horizontal platform to the drive means, and require two or more rollers on each side of the platform, to keep the platform horizontal during its rectangular path of travel. U.S. Pat. No. 4,214,848 is representative of prior art having an offset track and guide means to support a cantilevered platform.
Where the platform is rigidly secured to the drive means, as disclosed in U.S. Pat. No. 4,273,234, the platform does not remain horizontal during its rectangular path of travel. The platform must be pivotally mounted to the drive means, to maintain a horizontal position during the upward, backward, downward, and forward paths of travel.
Where the horizontal platform is supported by a drive means on the forward and rearward sides of the horizontal platform, as noted in U.S. Pat. No. 4,465,177, the drive means extends along both the forward path of travel on one side of each horizontal platform, and along the rearward path of travel on the opposite side of each platform. This limits access on one side of the horizontal platform at the inlet and outlet conveyers. U.S. Pat. No. 4,465,177 does not disclose a cantilevered horizontal platform, nor does U.S. Pat. No. 4,465,177 solve the problems associated with the resultant forces imposed upon the drive means by a cantilevered horizontal platform.